Cassini rose to prominence as society columnist for William Randolph Hearst's New York Journal-American. Writing under the name Cholly Knickerbocker, he was credited with coining the term "jet set" and helping spark a national fascination with Jacqueline Bouvier, the future wife of John F. Kennedy.

In 1947, when Bouvier was 17, Cassini dubbed her debutante of the year and described her as a "regal brunette, who has the classic features and the daintiness of Dresden porcelain."

He noted that the popular Bouvier had "poise, is soft-spoken and intelligent, everything the leading debutante should be." Later, when Jacqueline Kennedy was first lady, brother Oleg gained fame as her designer.

From 1953 to 1954, Igor Cassini had his own interview show on the now-defunct Dumont TV network.

But he ran into trouble in the early '60s, when an investigation by the Saturday Evening Post revealed he had served as a public relations agent for the Dominican Republic's longtime dictator, Rafael Trujillo, without properly registering as a foreign agent. Trujillo was assassinated in 1961.

The investigation caused Cassini to resign from his job as Knickerbocker.

Born in Russia, Cassini was the second son of an aristocratic family under the last czar. The family was forced to flee to Italy during the Russian Revolution.

Cassini and his brother later came to the United States, where they both became intrigued by Hollywood. Oleg Cassini first became established as a designer of costumes for the movies.

Cassini is survived by four children and his brother. A private funeral was scheduled for Wednesday.